Safavid era (1501-1736 A.D.) was one of the most important epochs in the history of Iran, because Iran experienced stability in it, the era of manifestation of the architectural skills. Sheikh Lotfollah Mosque is one of these manifestations. Another Islamic world empire was Ottoman Empire (1299-1923 A.D.). The mosques that were built for kings can be considered as perfect examples of outstanding architecture and aesthetical tradition of those eras. Suleymaniyeh Mosque is one of these mosques. Both empires had their special religious beliefs and reflection of these influences can be seen in their art and architecture. This study, by analytic- descriptive method, has focused on manifestation of religious beliefs in Iranian and Ottoman architecture, Sheikh Lotfollah Mosque Isfahan and Suleymaniyeh Mosque in Istanbul. The research shows that religious beliefs of rulers and worldview of their builders are hidden in their architectures, and adhering to religious is the cornerstone of both empires. The influence of religion was more notable on Safavid art and architecture. This is maybe due to long life of Ottoman Empire; on other hand the culmination of religious influence on Safavid art was coincided by the tolerance of Ottoman Empire with regard to other religions. The architect at the court of Ottoman Empire was first Christian, and maybe that is why Suleymaniyeh Mosque manifests the influence of Christianity along with of Sunni Islam; whereas Sheikh Lotfollah Mosque was representing Shiite and Sufism thoughts.